Tubulous vapor generating and superheating units



June 9, 1964 G. MCLAGAN KELLx-:T

TUBULOUS VAPOR GENERATING AND SUPERHEATING UNITS 4 Sheets-Sheet 1 FiledMarch 16, 1962 /N VEN 70K Gordon Mc Lagan Kelle'r A TTOE/VEY June 9,1964 G, MGLAGAN KELLET 3,136,301

TUBULOUS VAPOR GENERATING AND SUPERHEATING UNITS Filed March 16, 1962 4Sheets-Sheet 2 1o 29 T V I June 9, 1964 G, MCLAGAN KELLET 3,136,301

TUBuLoUs VAPOR GENERATING AND SUPERHEATING UNITS F11-ed Maron 1e, 1962 4sheets-sheet s June 9, 1954 G. MCLAGAN KELLET TUBULOUS VAPOR GENERATINGAND SUPERHEATING UNITS 4 Sheets-Sheet 4 Filed March 16, 1962 FLg.

l X i l x x l K x RK x l l x l I xi United States Patent 3,136,301TUBULOUS VAPOR GENERATING AND SUPERHEATING UNITS Y Gordon McLaganKellet, London, England, assigner to Babcock & Wilcox, Limited, London,England, a company of Great Britain Filed Mar. 16, 1962, Ser. No.180,241 Claims priority, application Great Britain Mar. 24, 1961 4Claims. (Cl. 122-480) This invention relates to vapor generating andsuperheating units, an object being the provision of an improvedsuperheater arrangement applicable to marine boilers.

Superheating means for a marine boiler have to meet various requirementsamong which is the necessity that the superheating means shall notinvolve any unnecessary use of space while it is very desirable toprovide for ready renewal of low temperature superheater tubes,

A tubulous vapor generating and vapor heating unit according to thepresent invention includes a bank of tubes extending across a gaspassage and forming two low ternperature superheater vapor passes in thefirst of which the tubes extend between an inlet header and a transferheader disposed atthe same side of the tube bank as the inlet header andin the second of which the tubes extend between the transfer header andan intermediate header dis posed at the side of the tube bank remotefrom the transfer header adjacent a high temperature superheater andserving as an inlet header to the high temperature superheater.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIGURE l is an elevation of a marine boiler in section on the line I-Iof FIGURE 2;

FIGURE 2 is a plan of the boiler in section on line Y II--II of FIGUREl;

VFIGURES 3 and 4 are plans of part of the boiler including thesuperheaters thereof in sections respectively on the lines III--III andIV-IV of FIGURE 1, and

FIGURE 5 shows schematically, in perspective fashion, the components ofthe superheaters to illustrate the relative positions which they bear toone another in the boiler,

' positioned. Two parallel gas ilow paths 5 and 6, separated by avertical division wall 7, lead the gases laterally from the furnacechamber below a horizontally arranged upper steam and water drum 8 andabove a horizontally arranged water drum 9, the front gas ilow path 5containing superheating surfaces which will be subsequently referred to,which surfaces are followed in the direction of gas ow by a bank 10 ofsteam generating tubes vertical over most of their lengths and extendingbetween the upper drum 8 and the lower drum 9, and the rear gas ow pathcontaining banks 11, 12 and 13 in succession in the direction of gasilow each of steam generating tubes extending between the upper drum 8and the lower drum 9. i

Between the furnace chamber and the parallel gas paths is a screen 14extending from front to rear of the furnace chamber, comprising twostaggered rows of steam generating tubes extending between the upperdrum 8 and a horizontally arranged header 15 having its axis below theaxis of the lower drum 8 and connected by connectors 21 to the lowerdrum 9; The furnace Patented June 9, 1964 ylower end of said wall, whichheader is connected to the header 15 by front and rear connectors ofwhich the rear connector 25 serves as'the lower header for steamgenerating tubes 26 cooling the rear wall of the furnace chamber andextending between the upper drum 8 and said connector 25. j

The -gases of the front'v gas ow path on leaving the steamgenerating'tube bank 10 and the gases of the rear gas ilow path onleaving the steam generating tube bank 13 enter respective spaces 27 and28 between theV said banks4 and a side wall 29 of the boiler. A platewall 30, uncooled, extends the vertical division wall 7 and reaches tothe side wall 24 and separates the spaces 27 and 28, which communicatewith the ships stack (not shown) through respective passages leadingupwardly to the side of the upper drum 8 and containing respectiveeconomizer surfaces; the passage 31 leading upwardly from the frontspace 27 and containing economizer surfaces 32 is shown in FIGURE l.These passages contain respective dampers, the dampers in the passage 31being denoted by the reference numeral 33.

The complete boiler is enclosed in a casing 34, spaced outwardly vfromthe various walls defining the furnace Vchamber and the gas flow paths.To the space 35 between the casing 34 and the said walls a ow of coolingair is supplied, which enters the furnace chamber 1 through the firingports 3 as combustion air. The necessary downcomer pipes 36 between thewater space of the upper steam andwater drum 8 and the water drum 9 areaccommodated in said space 35.

The superheating surfaces referred to, located in the front gas flowpa-th 5 between the screen 14 and the steam generating tube bank 10, arearranged to form a high temperature superheater 41 rst contacted by thehot gases in the said gas flow path and a low temperature superheater 42behind the high temperature superheater ,insaid gas flow path. The lowtemperature superheater 42 comprises an upper section 42a providing afirst steam pass-and a lower section 42b providing a second steam pass.l

The upper low temperature superheat section 42a comprises horizontalstraight tube limbs arranged in vertical vrows side by side. Each tubeprovides a plurality of tube limbs and extends in a horizontal plane;each tube is connected at its inlet end to an upright inlet header'43which is located to the front of the gas flow path'5, vextends severaltimes to and fro in sinuous fashion across the gas flow path 5 and isconnected at its outlet end to an upright transfer header 44 alsolocated to the front 0f the gas flow path 5. The inlet header 43 isdisposed to the side of the low temperature superheater remote from thefurnace chamber 1 and does not extend over the height of the lower lowtemperature superheater section 42b. The

transfer header 44 is also disposed to the side of the low temperaturesuperheater remote from the furnace chamber 1 and extends over the wholeheight of the low temperature superheater, the upper part of thetransfer header 44 receives the steam from the tubes of the upper lowtemperature superheater section 42a and the lower part thereof isarranged to pass the steam to the lower low temperature section 42b.

The lower low temperature superheater section 42b comprises horizontalstraight tube limbs arranged in vertical rows side by side. Each tubeprovides a plurality of tube limbs and extends in a horizontal plane;each tube is connected at itsinlet en d to the lower part of thetransfer header 44, extends several times to and fro in sinuousv fashionacross the gas flow path 5 and is connected at its outlet end to anupright intermediate header 45 also located to the front of the gas flowpath 5 and adjacent the high temperature superheater 41. Theintermediate header 45 is disposed to the side of the low temperaturesuperheater 42 nearer to the high ternperature superheater 41 and to theside `of that superheater remote from the furnace chamber 1.

Each tube of the lower low temperature superheater section 4212vcomprises alpair of straight limbs 46'connected by a return bend 47 anda pair of straight limbs 48 connected by a return bend 49, the adjacentlimbs of the two pairs being connected by a return bend 50; thus eachtube is of approximately W shape. There are two tubes of the lowerY,section 42b in each horizontal tube plane. Each tube of the uppersection 42a also comprises straight limbs 51 similar to the limbs 46 andstraight limbs v52 similar to the limbs 48, connected in series byreturn bends 53, 54 and 55 similar respectively to the tube bends 47, 49and 50 but for each tube of the upper section 42a an additional returnbend 56, connecting together tube limbs 52 remote from the inlet andtransfer headers, is provided so that the steam flows rst in a generaldirection towards the furnace chamber and then in the reverse sense;each tube of the upper section'42a includes all the tube limbs in thesame horizontal plane and these comprise twice the number of limbs asatube of the lower section.

The low temperature superheater 42 has the same vertical tube pitch andthe same tube bore throughout. The height of the upper section 42athereof is double the height of the lower section 42b thereof but byvirtue of the described tube arrangements the number of tubes in eachsection is the same and therefore the mass ow rate through the tubes isthe same throughout the low temperature superheater.

The high temperature superheater 41 comprises a lower section 41aproviding a first steam pass and an upper section 41b providing a secondsteam pass and al1 the tubes thereof extend between the mentionedintermediate header which extends throughout the height of the hightemperature superheater and a second transfer header 61 which alsoextends throughout the height of the high Vtemperature superheater andis disposed to the side of the said superheater nearer the furnacechamber.

The lower high temperature superheater section 41a comprises horizontaltube limbs arranged in verticalrows side by side. Each tube provides aplurality of tube limbs and extends in a horizontal plane. Each tube isconnected at its inlet end Vto the lower part or connecting section ofthe intermediate header 45, extends several times tov and fro in sinuousfashion across the gas ow path 5 in a Ageneral direction towards thefurnace chamber and is connected at its lower end to the lower part ofthe second transfer header 61. The upper high ternperature superheatersection 41b comprises horizontal tube limbs arranged in vertical rowsside by side. Each tube thereof provides a plurality of tube limbs andextends in a horizontal plane; each tube is connected at its inlet endto the upper part of the second transfer header 61, extends to and froin sinuous fashion across the gas ow path in a general direction awayfrom the furnace chamber andis connected at its outlet end to the upperpart or outlet section of the intermediate header 45. Within theintermediate header 45 is a diaphragm 62 separating the lower partthereof from the upper part thereof, from which latter the superheatedsteam is taken to the desired point of use. Y

The high temperature superheater 41 has the same tube pitch and the sametube diameter throughout and the heights of the upper and lower sections41b and '41a are the same. The vertical extent of the lower part of theintermediate header 45 is greater than the vertical extent of the lowersection42b of the 10W temperature superheater and the diaphragm 62 inthe intermediate header is substantially spaced above the points,indicated by 62, of entry into the said header of the'tubes of the lowtemperature superheater section 42h.

The low temperature superheater tubes are expanded i into the headerstherefor, that is to say, into the inlet header 43, the transfer header44 and the intermediate header 45. The high temperature superheatertubes are, however, weldedfthrough nipples to the headers therefor, thatis to say, to the intermediate header 45 and the second transfer header61.

Refractory 64 associated with upper and lower parts of tubes of thescreen 44 ensure that gases in the front gas flow path 5 do not bypassthe superheating surfaces.

The superheater tubes are supported by any suitable means, which mayinclude, for the tube parts remote from the headers, supports 65 ofknown kind secured to a tube of the tube screen 14 and to three tubes 66extending between the drums 8 and 9.

In the operation of the boiler, the steam generatedy in the varioussteam generating tubes when the furnace chamber 1 is fired is separatedfrom water in the upper vdrum 8 and is led tothe low temperaturesuperheater inlet header 43 whence it flows through the tubes of thelower temperature superheater upper section 42a to the upper part ofthevtransfer header 44. In the transfer header the steam flows into thelower part thereof and thence through the tubes of the low temperaturesuperheater lower section to the lowermost part of the intermeditaeheader 45. The steam lls the Whole of the lower part of the intermediateheader V45 below the diaphragm 62 and flows thence through the tubes ofthe high temperature superheater lower section 41a to the lower part ofthe second transfer header 61. In the second transfer header the steamflows into the upper part thereof and thence through the tubes of thehigh temperature superheater upper part 41b to the upper part of theintermediate 'header 45. A high temperatureV of superheat is available,.since the high temperature superheater 41 is separated from the furnacechamber simply by the screen 44 of steam generating tubes. Superheattemperatures may be regulated by control through adjustment 'of thedampers of the distribution of the gas flow from the furnace-chamberbetween the gas flow paths 5 and 6.

Y Since the lower section of the intermediate header 45 serves as theconnection between the low temperature and the high temperaturesuperheaters 42 and 41, the arrangement avoids the use of one outletheader for the low temperature superheater and a Vseparate inlet headerparallel thereto for the high tempertaure superheater, the connectionbetween which has frequently consisted of a large diameter pipe whichinvolves an undesirable degree of rigidity between the two headersunless a bulky expansion loop is included therein, and which moreover,is likely to enforce a high minimum spacing between the low temperatureand the high temperature superheaters. As it is, the spacing between thetwo superheaters 41 and 42 is no more than that required to afford thedesired access space therebetween.

The space between the two superheaters is entered by a workman whennecessary, when the boiler is cold, through an access opening 67 in thefront wall of the front gas ilow path 5. Y

During a reft, tubes of the low temperature superheater or of the hightemperature superheater may be replaced as necessary without disturbingthe various headers, which are not in the way of forward withdrawal offailed superheater tubes, after they have been cut out, through thefront wall of the gas flow path 5 and through the casing 34 whenappropriate panels therein, not indicated, have been removed and whichare similarly not in the way of the subsequent rearward insertion offresh superheater tubes.

The disposition of the second transfer header 61 to the u side of thehigh temperature superheater nearer the furadvantage accrues owing tothe disposition of the intermediate header 45 to the side of the highertemperature superheater remote from the furnace chamber.

The pipework connections to the inlet header 43 and from the outletsection of the intermediate header 45 are easily arranged since thesetwo headers are not immediately adjacent one another.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form and mode of operation ofthe invention now known to me, those skilled in the art will understandthat changes may be made in the form of the apparatus disclosed withoutdeparting from the spirit of the invention covered by my claims, andthat certain features of my invention may sometimes be used to advantagewithout a corresponding use of other features.

The claims are:

l. In a vapor generating superheating unit, Walls including vaporgenerating tubes forming a furnace, a gas pass leading from the furnace,a superheater disposed in and extending across said gas pass andcomprising a first bank of looped tubes forming two low temperaturesuperheater vapor passes situated one directly above the other, a secondbank of looped tubes disposed upstream gas-fiow wise of said first bankof looped tubes and forming two high temperature superheater vaporpasses situated one directly above the other, an inlet header disposedto the side of said first tube bank farthest from the furnace andconnected for flow of fluid from the vapor generating tubes, a firsttransfer header disposed at the same side of the first tube bank as theinlet header, an intermediate header divided into two sections anddisposed at the side of the first tube bank nearest to the furnace andadjacent to the side of said second tube bank farthest from the furnace,a second transfer header disposed to the side of said second tube banknearest to the furnace, the tubes of one of the low temperaturesuperheater vapor passes extending between and directly connected to theinlet header and the first transfer header, the tubes of the other lowtemperature superheater vapor pass extending between and directlyconnected to the first transfer header and one of the sections of theintermediate header, the tubes of one of the high temperaturesuperheater vapor passes extending between and directly connected tosaid one section of the intermediate header and the second transferheader, and the tubes of the other high temperature superheater vaporpass extending between and directly connected to said second transferheader and the other section of said intermediate header.

2. In a vapor generating superheating unit, walls including vaporgenerating tubes forming a furnace, a gas pass leading from the furnace,a superheater disposed in and extending across the gas pass andcomprising a first bank of horizontally extending looped tubes formingfirst and second low temperature superheater vapor passes, a second bankof horizontally extending looped tubes disposed upstream gas-flow wiseof said rst bank of looped tubes and forming first and second hightemperature superheater vapor passes, the tubes of the first lowtemperature vapor pass being situated directly above the tubes of thesecond low temperature vapor pass, the tubes of the first hightemperature vapor pass being situated directly below the tubes of thesecond high temperature vapor pass, an upright inlet header disposed tothe side of the first tube bank farthest from the furnace and connectedfor fiow of fluid from the vapor generating tubes, an upright firsttransfer header disposed at the same side of the first tube bank as theinlet header, an upright intermediate header divided into upper andlower sections and disposed at the side of the first tube bank nearestto the furnace and adjacent to the side of the second tube bank farthestfrom the furnace, an upright second transfer header disposed to the sideof said second tube bank nearest to the furnace, the tubes of the firstlow temperature vapor pass extending between and directly connected tothe inlet header and the first transfer header, the tubes of the secondlow temperature vapor pass extending between and directly connected tothe first transfer header and the lower section of the intermediateheader, the tubes of the first high temperature vapor pass extendingbetween and directly connected to the lower section of the intermediateheader and the second transfer header, and the tubes of the second hightemperature Vapor pass extending between and directly connected to thesecond transfer header and the upper section of the intermediate header.

3. A unit as claimed in claim 1, wherein in the first bank of tubesforming the two low temperature superheater vapor passes the tube pitchand the tube bores and the number of rows of tube limbs transverse tothe gas flow are the same throughout the tube bank while the numbers oftubes in the two passes are chosen to give equal or approximately equalmass flows of vapor throughout the tubes of the bank.

4. A unit as claimed in claim 1 wherein the tubes of the first lowtemperature vapor pass comprise one group of adjacent tubes and thetubes of the second low ternperature vapor pass comprise another groupof adjacent tubes of the tube bank, the tubes of the first lowtemperature vapor pass occupying approximately two thirds of thedistance between opposite boundaries of the gas pass and the tubes ofthe second low temperature vapor pass occupying the remainder of thedistance.

References Cited in the file of this patent UNITED STATES PATENTS2,939,435 Ressler June 7, 1960 FOREIGN PATENTS 58,455 Netherlands Nov.15, 1946 291,507 Great Britain June l, 1928

1. IN A VAPOR GENERATING SUPERHEATING UNIT, WALLS INCLUDING VAPORGENERATING TUBES FORMING A FURNACE, A GAS PASS LEADING FROM THE FURNACE,A SUPERHEATER DISPOSED IN AND EXTENDING ACROSS SAID GAS AND COMPRISING AFIRST BANK OF LOOPED TUBES FORMING TWO LOW TEMPERATURE SUPERHEATER VAPORPASSES SITUATED ONE DIRECTLY ABOVE THE OTHER, A SECOND BANK OF LOOPEDTUBES DISPOSED UPSTREAM GAS-FLOW WISE OF SAID FIRST BANK OF LOOPED TUBESAND FORMING TWO HIGH TEMPERATURE SUPERHEATER VAPOR PASSES SITUATED ONEDIRECTLY ABOVE THE OTHER, AN INLET HEADER DISPOSED TO THE SIDE OF SAIDFIRST TUBE BANK FARTHEST FROM THE FURNACE AND CONNECTED FOR FLOW OFFLUID FROM THE VAPOR GENERATING TUBES, A FIRST TRANSFER HEADER DISPOSEDAT THE SAME SIDE OF THE FIRST TUBE BANK AS THE INLET HEADER, ANINTERMEDIATE HEADER DIVIDED INTO TWO SECTIONS AND DISPOSED AT THE SIDEOF THE FIRST TUBE BANK NEAREST TO THE FURNACE AND ADJACENT TO THE SIDEOF SAID SECOND TUBE BANK FARTHEST FROM THE FURNACE, A SECOND TRANSFERHEADER DISPOSED TO THE SIDE OF SAID SECOND TUBE BANK NEAREST TO THEFURNACE, THE TUBES OF ONE OF THE LOW TEMPERATURE SUPERHEATER VAPORPASSES EXTENDING BETWEEN AND DIRECTLY CONNECTED TO THE INLET HEADER ANDTHE FIRST TRANSFER HEADER, THE TUBES OF THE OTHER LOW TEMPERATURESUPERHEATER VAPOR PASS EXTENDING BETWEEN AND DIRECTLY CONNECTED TO THEFIRST TRANSFER HEADER AND ONE OF THE SECTIONS OF THE INTERMEDIATEHEADER, THE TUBES OF ONE OF THE HIGH TEMPERATURE SUPERHEATER VAPORPASSES EXTENDING BETWEEN AND DIRECTLY CONNECTED TO SAID ONE SECTION OFTHE INTERMEDIATE HEADER AND THE SECOND TRANSFER HEADER, AND THE TUBES OFTHE OTHER HIGH TEMPERATURE SUPERHEATER VAPOR PASS EXTENDING BETWEEN ANDDIRECTLY CONNECTED TO SAID SECOND TRANSFER HEADER AND THE OTHER SECTIONOF SAID INTERMEDIATE HEADER.